biting midges — wirth and blanton 243 



Life Zones in Panama 



There are three principal life zones in the Republic of Panama — 

 tropical, subtropical, and temperate (Goldman, 1920; Griscom, 1935). 



The tropical zone covers nearly the entire country except for some 

 elevations above 3,000 to 3,500 feet. It is divided by rainfall differ- 

 ences into two sections, the humid tropics (lowland rain forest) on 

 the entire Atlantic slope and on the Pacific side of eastern Darien, 

 and the arid tropics (arid deciduous forest and savanna) on the 

 remaining Pacific slope. 



In the humid tropical zone the annual rainfall ranges up to 150 

 inches, and although it comes mostly in the wet season, enough falls 

 regularly in the dry season to support an evergreen or rain forest 

 (Standley, 1928). Plants forming the characteristic vegetation in- 

 clude the star-apple (Chrysophyllum) , wild fig (Ficus), almendro 

 (Dipteryx panamensis), maragua {Poulsenia armata), and many 

 palms, aroids, heliconias, and lianas. Characteristic mammals are 

 tapirs, monkeys, cats, opossums, squirrels, and arboreal anteaters 

 and sloths. 



In the arid tropical zone the rainfall is less, about 85 inches in the 

 wet season, and the long drought causes the forest to turn brown and 

 lose its leaves except in the stream valleys. In western Panama 

 there are, or were before deforestation by man, extensive areas of 

 ^ open or gallery forest along the coastal border, with trees of impressive 

 size. Farther inland there is a belt of low scrub forest interrupted 

 by areas of open grassland or savannas, which are frequently burned 

 over during the dry season. Farther up the slopes of the mountains 

 the forest reappears and becomes better developed. In eastern 

 Panama, merging into the Pacific or South American rain forest, 

 there is a different type of gallery forest, such as that in the Tuyra 

 River valley, called by Griscom (1935) the cuipo forest, with a fauna 

 all its own. Plants characteristic of the arid tropics of Panama are 

 the guarumo {Cecropia arachnoides) , cuipo (Cavanillesia) , cocobola 

 {Dalbergia retusa), Spanish cedar (Cedrela), guava (Psidium guajava), 

 mesquite (Prosopis), cacti, and many grasses and sedges. Charac- 

 teristic mammals include peccaries, forest rabbits, foxes, and deer. 



The subtropical zone (montane rain forest) comprises the upper 

 slopes and crests of the mountains between 3,000 and 8,500 feet 

 elevation, only the Volcdn de Chiriqui rising above this zone. This 

 zone is forested, with many palms and tree ferns, the trees being 

 generally smaller than in the tropical zone, with great variations in 

 kinds due to slope exposure. Precipitation and fogs in a cloud belt 



